This invention relates to an underground pipe pusher for forcing pipe into the ground by a piercing tool.
It has been found that underground piercing tools, such for example, as disclosed in U.S. Pat. No. 3,410,354, issued on Nov. 12, 1968, can be fitted with an adaptor arranged to engage the end of a pipe whereby impacting action upon the piercing tool will drive the pipe forward into the ground. Such a method can provide economic gains over conventional ground boring machines in the matter of initial equipment cost, set-up time, and overall pipe installation time.
Such adaptors, as presently used, are formed with an internal tapered bore to match the taper of the piercing tool head end, and an external tapered surface to wedge into the end of the pipe to be pushed. Such wedging arrangement is required so that the pipe, adaptor and piercing tool are coupled together as a unit to withstand the percussive action and reaction to which the piercing tool is subjected during pipe driving action.
The inherent disadvantage of the current arrangement above described, is that the end of the pipe being driven is flared out by the adaptor, often necessitating cut-off if additional pipe is to be driven thereagainst.
In situations where the driven pipe has an exterior threaded end surface, the adaptor will have a threaded portion for connection to the pipe. Impacting action on the adaptor can damage the pipe threads, thus making connection with an adjoining pipe less effective, or even impossible if thread damage on the driven pipe is excessive.
Also, at times, the pipe adaptor, and piercing tool are wedged together so tight that time consuming effort is required for separation thereof.
The present invention, while having all the advantages of the adaptors in use as explained above, avoids the functional shortcomings thereof. For example, the adaptor disclosed herein, will not flare or otherwise damage the end of the pipe being driven, nor will the threads at the end of a threaded pipe be damaged by impact forces upon the adaptor. Furthermore, the wedge grip between the pipe, adaptor, and piercing tool, can be easily released by application of impact loading upon the piercing tool in a direction away from the adaptor.